Transmission path identification based on propagation channel diversity

ABSTRACT

Various embodiments of the present technology relate generally to wireless power systems. More specifically, some embodiments relate to the use of time reversal techniques utilizing time diversity (e.g., different multipath arrivals at the same antenna) to achieve coherency from the same transmission node. For example, instead of initiating outgoing transmissions (e.g., power signals) at the same time, various embodiments can initiate the outgoing signals from the various antennas in a staggered timing that is a reversal of the arrival times of an incoming signal. As a result of staggering the start of the outgoing signals, the signals will arrive at the destination at approximately the same time even though they have traveled different paths having different propagation delays.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/852,348, filed on Dec. 22, 2017, and issued as U.S. Pat. No.10,418,861 on Sep. 17, 2019, which is incorporated herein by referencein its entirety.

BACKGROUND

Many electronic devices are powered by batteries. Rechargeable batteriesare often used to avoid the cost of replacing conventional dry-cellbatteries and to conserve precious resources. The requirements ofcompact and faster devices that are enabled with standard wirelesscommunication modules such as LTE, Wi-Fi, and Bluetooth transceivershave become a basic standard of modern mobile devices. Today'sinformation-oriented users demand more sophisticated applications, andare in need to be connected constantly. These rising demands requiremore computational and transmission power which leave batteries thirstyfor charge.

Rechargeable batteries are one option. However, conventionalrechargeable battery chargers often require access to a power sourcesuch as an alternating current (AC) power outlet, which may not alwaysbe available or convenient. Current techniques for wireless charginghave been limited to magnetic or inductive charging based solutions.Unfortunately, these solutions require a wireless power transmissionsystem and a receiver to be in relatively close proximity to oneanother. Wireless power transmission at larger distances often uses moreadvanced mechanisms such as, for example, transmission via radiofrequency (RF) signals, ultrasonic transmissions, laser powering, toname a few, each of which present a number of unique hurdles tocommercial success.

Systems that support wireless power transmission at larger distances mayuse sophisticated signal transmitting (Tx) and receiving (Rx)components. Precisely locating components in the environment anddetermining signal transmission paths therein is a prerequisite toproviding Tx radiation patterns and targeting client Rx devices forefficient data communication and/or wireless power delivery. Further, insuch systems, accurate location determinations of Tx and/or Rx devicesin a dynamic environment is necessary to ensure effective anduninterrupted service. Efficiently computing such transmission paths anddevice locations can be challenging.

Accordingly, a need exists for technology that overcomes the problemdemonstrated above, as well as one that provides additional benefits.The examples provided herein of some prior or related systems and theirassociated limitations are intended to be illustrative and notexclusive. Other limitations of existing or prior systems will becomeapparent to those of skill in the art upon reading the followingdetailed description.

SUMMARY

Various embodiments of the present technology relate generally towireless power systems. More specifically, some embodiments relate totransmission path identification based on propagation channel diversity.For example, various embodiments of the present technology use timereversal techniques based on arrival time diversity (e.g., differentphase of arrivals at the same antenna) of signaling within a multipathenvironment and achieve coherency from the same transmission node.

In some embodiments, a wireless signal (e.g., a beacon signal) can bereceived from a client device. The wireless signal transmitted from theclient device can take multiple paths and therefore arrive at the arrayof antennas at different times. The time of arrival of the wirelesssignal at each antenna in the array of antennas can be determined. Then,a coherent transmission signal can be generated and sent to the clientdevice from the array of antennas. The coherent transmission signal canbe created by transmitting the signals which are time reversed versionsof the incoming signals at each antenna. Some embodiments can record amagnitude and/or phase of the wireless signal received at each antennain the array of antennas. In addition, generating the coherenttransmission signal can include adjusting corresponding magnitudes ofthe coherent transmission signal in the array of antennas. The array ofantennas can be an adaptively-phased antenna array in some embodiments.

Embodiments of the present technology also include computer-readablestorage media containing sets of instructions to cause one or moreprocessors to perform the methods, variations of the methods, and otheroperations described herein.

Some embodiments provide for a wireless power transmission system thatincludes a memory, one or more processors, an adaptively-phased antennaarray, control circuitry, a signal generator, a pattern matching engine,and/or other components. The antenna array can have multiple radiofrequency (RF) antennas. The control circuitry can be operativelycoupled to the multiple RF antennas. In addition, the control circuitrycan monitor arrival of a wireless signal from a client device at each ofthe RF antennas in the antenna array. An arrival profile can then begenerated based, at least in part, on the arrival of the wireless signalat each RF antenna in the antenna array. The control circuitry can thensend, from the antenna array, a transmission signal to the client devicereversing the received wireless signal. This can be done, in someembodiments, without any direct time of arrival measurements. Thecontrol circuitry can record, in the memory, at least a portion of thewireless signal in the time domain and identify an arrival sequence. Thewireless signal is in a multipath environment and the control circuitrymonitors for multiple arrivals of the wireless signal at different timesand samples the incoming wireless signal at each antenna in the antennaarray. The signal generator can process the wireless signal and generatethe transmission signal. The pattern matching engine can identify theincoming signal.

While multiple embodiments are disclosed, still other embodiments of thepresent technology will become apparent to those skilled in the art fromthe following detailed description, which shows and describesillustrative embodiments of the technology. As will be realized, thetechnology is capable of modifications in various aspects, all withoutdeparting from the scope of the present technology. Accordingly, thedrawings and detailed description are to be regarded as illustrative innature and not restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present technology will be described and explainedthrough the use of the accompanying drawings.

FIG. 1 is a diagram illustrating an example wireless communication/powerdelivery environment that may be utilized in one or more embodiments ofthe present technology.

FIG. 2 is a block diagram illustrating an example transceiver system inaccordance with various embodiments of the present technology.

FIG. 3 is a block diagram illustrating an example client receiver inaccordance with one or more embodiments of the present technology.

FIG. 4 is a sequence diagram illustrating example operations between awireless power transmission system and a wireless receiver client forcommencing wireless power delivery in accordance with some embodiments.

FIG. 5 illustrates an example multipath wireless power deliveryenvironment according to some embodiments of the present technology.

FIG. 6 is a flowchart illustrating a set of operations for operating awireless communication/power delivery system in accordance with someembodiments of the present technology.

FIG. 7 is a sequence diagram illustrating an example of the data flowbetween various components of a wireless power transmission systemcomponents according to various embodiments of the present technology.

FIG. 8 depicts a diagrammatic representation of a machine, in an exampleform, of a computer system within which a set of instructions, forcausing the machine to perform any one or more of the methodologiesdiscussed herein, may be executed.

The drawings have not necessarily been drawn to scale. Similarly, somecomponents and/or operations may be separated into different blocks orcombined into a single block for the purposes of discussion of some ofthe embodiments of the present technology. Moreover, while thetechnology is amenable to various modifications and alternative forms,specific embodiments have been shown by way of example in the drawingsand are described in detail below. The intention, however, is not tolimit the technology to the particular embodiments described. On thecontrary, the technology is intended to cover all modifications,equivalents, and alternatives falling within the scope of the technologyas defined by the appended claims.

DETAILED DESCRIPTION

Various embodiments of the present technology relate generally towireless power systems. More specifically, some embodiments relate totransmission path identification based on propagation channel diversity.Traditional retrodirective phased array systems utilize the spatialdiversity (e.g., different phase of arrivals measured at differentantennas) and try to achieve coherency from different transmissionnodes. In contrast, various embodiments of the present technology usetime reversal techniques based on arrival time diversity (e.g.,different phase of arrivals at the same antenna) and achieve coherencyfrom the same transmission node.

For example, instead of initiating outgoing transmissions (e.g., powersignals) at the same time, various embodiments can initiate the outgoingsignals from the various antennas based on a reversal of the arrivaltimes of an incoming signal. As a result of staggering the start of theoutgoing signals, the signals will arrive at the destination atapproximately the same time even though they have traveled differentpaths having different propagation delays. Such techniques candrastically reduce power consumption on both the transmitting andreceiving devices.

In the following description, for the purposes of explanation, numerousspecific details are set forth in order to provide a thoroughunderstanding of embodiments of the present technology. It will beapparent, however, to one skilled in the art that embodiments of thepresent technology may be practiced without some of these specificdetails. While, for convenience, embodiments of the present technologyare described with reference to wireless power transmission systems andclient receivers, embodiments of the present technology are equallyapplicable to various computing technologies using antenna arrays.

The techniques introduced here can be embodied as special-purposehardware (e.g., circuitry), as programmable circuitry appropriatelyprogrammed with software and/or firmware, or as a combination ofspecial-purpose and programmable circuitry. Hence, embodiments mayinclude a machine-readable medium having stored thereon instructionswhich may be used to program a computer (or other electronic devices) toperform a process. The machine-readable medium may include, but is notlimited to, floppy diskettes, optical disks, compact disc read-onlymemories (CD-ROMs), magneto-optical disks, ROMs, random access memories(RAMs), erasable programmable read-only memories (EPROMs), electricallyerasable programmable read-only memories (EEPROMs), magnetic or opticalcards, flash memory, or other type of media/machine-readable mediumsuitable for storing electronic instructions.

The phrases “in some embodiments,” “according to some embodiments,” “inthe embodiments shown,” “in other embodiments,” and the like generallymean the particular feature, structure, or characteristic following thephrase is included in at least one implementation of the presenttechnology, and may be included in more than one implementation. Inaddition, such phrases do not necessarily refer to the same embodimentsor different embodiments.

FIG. 1 is a diagram illustrating an example wireless communication andpower delivery environment 100 depicting wireless power delivery anddata communication from one or more wireless transceiver systems 101 tovarious wireless client devices 102.1 to 102.4 within environment 100.Client power receivers 103.1 to 103.4 can be integrated into respectiveclient devices 102.1 to 102.4 and configured to receive wireless powerfrom the one or more transceiver systems 101. Within environment 100,the wireless delivery of power from transceiver system 101 to clientpower receivers 103.1 to 103.4 embedded in client devices 102.1 to 102.4is also referred to herein as a wireless power transfer system (WPTS).

As shown in the embodiments illustrated in FIG. 1, wireless clientdevices 102.1 to 102.4 can include mobile phone devices (e.g., clientdevice 102.3 having a respective client power receiver 103.3) andwearable electronics (e.g., client device 102.2 having a respectiveclient power receiver 103.2). Client devices 102 can be any wirelessdevice that needs power and capable of receiving wireless power via oneor more integrated client power receivers 103.1 to 103.4.

Client devices 102.1 to 102.4 can be enabled to communicate withtransceiver systems 101 and other communication devices (e.g., Wi-Fi andcellular networks). Client devices 102.1 to 102.4 can be further enabledto transmit beacon signals. Other client devices, not shown in FIG. 1,may not be configured and enabled to communicate (e.g., no Bluetooth orWi-Fi capability) and thus do not transmit beacon signals. The one ormore integrated power receiver clients, or “wireless power receivers,”can receive and process power from the one or more transceiver systems101 and provide the power to the client devices 102.1 to 102.4 foroperation thereof.

Each transceiver system 101 can include an antenna array having aplurality of antenna elements that are each capable of deliveringwireless power to client devices 102.1 to 102.4. Each transceiver system101 can also transmit (Tx) and receive (Rx) wireless data communicationsignals to and from client devices 102.1 to 102.4, respectively. In someembodiments, the data communication antennas can communicate viaBluetooth™, Wi-Fi, ZigBee™, or other wireless communication protocolssuch IEEE 802.15.4 or IEEE 802.11. Also, in some embodiments, thewireless power and wireless communication signals can be delivered as acombined power/communication signal. In still other embodiments, notshown in FIG. 1, transceiver system 101 can include an additionalantenna and/or an antenna array separate from the antenna array thatimplements data communication, but not wireless power delivery.

The transceiver system 101 can be configured to determine theappropriate phases to transmit coherent power signals 101.1-101.4 toclient power receivers 103.1 to 103.4 as part of the WPTS. The antennaarray can transmit a signal (e.g., a continuous wave or a pulsed powertransmission signal) from each of the plurality of antenna elements at aspecific phase relative to each other. Further, it is to be understoodthat use of the term “array” does not necessarily limit the antennaarray to any specific array structure. That is, the antenna array neednot be structured in a specific “array” form or geometry. Furthermore,as used herein, the term “array” or “array system” can be used toinclude related and peripheral circuitry for signal generation,reception, and transmission, such as in radios, digital logic, andmodems.

Each client power receiver 103.1 to 103.4 can include one or moreantennas (not shown) for receiving signals from the transceiver systems101. The antenna array can be capable of emitting continuous wavesignals at specific phases relative to each other. As discussed above,using an antenna array as a primary input device, transceiver system 101can determine the appropriate phases for delivering coherent signals tothe client power receivers 103.1 to 103.4. For example, coherent signalscan be determined by computing the complex conjugate of a receivedbeacon and/or other signal at each antenna element of the antenna arraysuch that the coherent signal is properly phased for the particularclient power receiver 103.1 to 103.4 that transmitted the beacon orother signal. The beacon signal and other signals described andillustrated, are primarily referred to herein as continuous waveforms,but alternatively or additionally take the form of modulated signalwaveforms.

Although not illustrated in FIG. 1, each of the above listed componentsof the environment 100 (e.g., client power receivers 103.1 to 103.4,transceiver system 101, etc.) can include control and synchronizationmechanisms, such as a data communication synchronization module. Thetransceiver systems 101 are connected to a power source such as, forexample, a power outlet or source connecting the transmitters to astandard or primary alternating current (AC) power supply in a building.Alternatively, or additionally, one or more of the transceiver systems101 can be powered by a battery or via another power-providingmechanism.

In some embodiments, the client power receivers 103 and/or thetransceiver systems 101 utilize or encounter reflective surfaces suchas, for example, walls or other RF reflective obstructions within rangeto beacon and deliver and/or receive wireless power and/or data withinwireless communication and power delivery environment 100. One or moreof the reflective surfaces can be utilized for multi-directional signalcommunication regardless of whether a blocking object is in the line ofsight between transceiver system 101 and client power receiver 103. As aresult, signals between the client power receivers and the transceiversystem 101 may take multiple paths each having different propagationdelays. Transceiver system 101 can record the incoming RF signal at thedifferent antennas in the antenna array (e.g., by a raw sampling). Therecordation of the arrival times for example can be used to construct anarray of absolute and/or relative times of arrival. Then, any outgoingsignaling to the client power receivers 103 can activate the antennaarray elements effectively reversing arrival times and achieve coherencyfrom the same transmission node.

As described herein, each client device 102.1 to 102.4 can be any systemand/or device, and/or any combination of devices/systems that canestablish a communication connection (e.g., session) with anotherdevice, a server and/or other systems within the example environment100. In some embodiments, the client devices 102.1 to 102.4 includedisplays or other output functionalities to present data to a userand/or input functionalities to receive data from the user. By way ofexample, a client device 102 can be, but is not limited to, a video gamecontroller, a server desktop, a desktop computer, a computer cluster, ora mobile computing device (such as a notebook, a laptop computer, ahandheld or tablet computer, a mobile phone, a smart phone, a battery orcomponent coupled to a battery, a PDA, etc.). The client device 102 canalso be any wearable device such as watches, necklaces, rings, or evendevices (e.g., medical or veterinary devices) implanted within a humanor animal patient. Other examples of a client device 102 include, butare not limited to, safety sensors (e.g., fire or carbon monoxide),electric toothbrushes, electronic door locks/handles, electric lightswitch controllers, electric shavers, etc.

Although not illustrated in the example of FIG. 1, the transceiversystem 101 and the client power receivers 103.1 to 103.4 can eachinclude a data communication module for communication via a datachannel. Alternatively, or additionally, the client power receivers103.1 to 103.4 can direct the client devices 102.1 to 102.4 tocommunicate with the transceiver system 101 via existing datacommunications modules.

FIG. 2 is a block diagram illustrating an example transceiver system 101in accordance with an embodiment (e.g., transceiver system 101 shown inFIG. 1). The transceiver system 101 can include various functionalcomponents such as analog and digital electronic devices that are atleast one of electrically and communicatively coupled together. In theembodiments shown in FIG. 2, antenna array 104 can include a pluralityof antenna elements 201 arranged within antenna array 104 with a fixedgeometry (not shown) relative to one another. In other embodiments,antenna array 104 includes one antenna element 201. In still otherembodiments, antenna array 104 includes a plurality of antenna elements201, but is capable of functioning in transceiver system 101 to performthe processes and methods described herein when only one element 201 isactually functioning for Tx, Rx, and/or power delivery.

As illustrated in FIG. 2, the functional components of transceiversystem 101 can include a processor 202 and a memory 204 (including,e.g., a non-transitory processor-readable medium). Memory 204 can storevarious types and classes of data generated through, for example, thesystems, methods, and processed described herein. Memory 204 can alsostore program instructions (e.g., software and/or firmware) that, whenexecuted by processor 202, cause the processor 202 to manipulate (e.g.,read, write, and delete operations, and combinations thereof) datastored in memory 204 and data stored in other transceiver system 101components (e.g., data stored in registers and other data storage mediathereof) associated with and/or communicatively coupled to processor 202and/or memory 204. Through these data manipulations and othercomputation-related actions of processor 202 (e.g., carried out by anarithmetic logic unit and/or CPU of processor 202), the programinstructions direct the implementation of the methods and processesherein described.

The various functionality described herein for processor 202 and/ormemory 204 may, in some embodiments, be carried out by substantiallysimilar components of a remote processor server 206 (e.g., networkedcloud server). For example, remote processor server 206 located somedistance from transceiver system 101 can include a remote processorserver 206 processor and a memory, not shown. For considerations such asspeed of data processing, amount and/or availability of data storage inmemory, and reducing the size of the transceiver system 101, remoteprocessor server 206 may entirely replace processor 202 and/or memory204 in transceiver system 101, or may supplement a fraction of thatfunctionality in transceiver system 101.

Transceiver system 101 may also include a network interface device 208which is capable of receiving and transmitting data over a wired orwireless network communications protocol, including data retrieved fromand/or stored in memory 204 that is received from and/or transmitted to,respectively, client 102 and/or a cloud-based application executed byone or more processors in a computing device of remote processor server206). Transceiver system 101 can also include a display device 212.User-friendly values (e.g., a processor 202-rendered 3D model ofenvironment 100) may be displayed on display device 212 that are visibleto a user and/or they may be transmitted to a computing device such as alaptop or desktop computer (not shown in FIG. 2) of the user that iscommunicatively coupled to transceiver system 101. Furthermore,transceiver system 101 includes a power supply 214 which providesappropriate levels of electric power to network interface device 208,antenna array 104, processor 202, and, as needed, memory 204.

In response to inputs and/or events including receipt of beacon signal324 at antenna array 104, processor 202 can execute the programinstructions to implement the methods and processes described herein. Ina multipath environment, the signals, 322, 324, and 327 betweentransceiver system 101 and client power receiver 103 can take multiplepaths each having a different propagation delay. As such, recorder 220can record arrival times of the signals at the different antennas.Reversal module 222 can reverse time to generate a replay of the signal.Using the time reversed signal, timing module 209 can activate antennaelements 201 in a reverse order to the arrival when sending an outgoingsignal (e.g., power signal 322). As a result, signals having paths withlonger propagation delays are sent first and the smallest propagationdelays sent last. This results in the signals arriving at thedestination device (e.g., client power receiver 103) at substantiallythe same time.

Additional events such as receipt, via network interface device 208, ofnetwork traffic 216 including data and/or other signals from a network218 further cause processor 202 to execute program instructions storedin memory 204 to implement processes and methods in transceiver system101, either instead of, or in addition to, the methods and processesherein described.

In the embodiments illustrated in FIG. 2, a computer system 222 includesprocessor 202 and memory 204. Various common components (e.g., cachememory) are omitted for illustrative simplicity. The computer system 222is intended to illustrate a hardware device on which the various processand methods described herein can be implemented. The components ofcomputer system 222 and other components of transceiver system 101 canbe coupled together via a power and data bus 224 or through some otherknown or convenient device.

The processor 202 shown in FIG. 2 may be, for example, a conventionalmicroprocessor, microcontroller, a field-programmable gate array (FPGA),and combinations thereof. One of skill in the relevant art willrecognize that the terms “processor-readable (storage) medium” or“computer-readable (storage) medium” include any type of device that isaccessible by processor 202. Memory 204 is communicatively coupled toprocessor 202 by, for example, a memory bus 226. In addition tonon-transitory media, the memory 204 can include, by way of example butnot limitation, random access memory (RAM), such as dynamic RAM (DRAM)and static RAM (SRAM). The memory 204 can be local, remote, ordistributed. Non-transitory (e.g., non-volatile) memory is often amagnetic floppy or hard disk, a magnetic-optical disk, an optical disk,a read-only memory (ROM), such as a CD-ROM, EPROM, or EEPROM, a magneticor optical card, or another form of storage for large amounts of data.Some of this data is often written, by a direct memory access process,into memory 204 during execution of program instructions by processor202. The non-volatile memory can be local, remote, or distributed.

Program instructions (e.g., software) are typically stored innon-volatile portions of memory 204 and/or a drive unit (not shown inFIG. 2). Indeed, for large programs, it may not even be possible tostore the entire program in the memory 204. Nevertheless, it should beunderstood that for software to run, if necessary, it is moved to aprocessor 202-readable location appropriate for processing, and forillustrative purposes, that location is referred herein to as the memory204. Even when software is moved to the memory 204 for execution, theprocessor 202 will typically make use of hardware registers to storevalues associated with the software, and further will cache those valueslocally to, ideally, speed up execution of program instructions andrelated operations with respect to memory 204. As used herein, asoftware program is assumed to be stored at any known or convenientlocation (from non-volatile storage to hardware registers) when thesoftware program is referred to as “executed by and implemented in aprocessor 202-readable medium,”, and similar terminology. A processorsuch as processor 202 is considered to be “configured to execute aprogram” when at least one value associated with the program is storedin a register readable by the processor.

The bus (e.g., data carrying portions of power and data bus 224) alsocouples the processor 202 and, optionally, the memory 204 to the networkinterface device 208. The network interface device 208 can include oneor more of a modem, a router, and a network interface (e.g., a networkinterface card (NIC)). It will be appreciated that a modem or networkinterface can be considered to be part of the computer system 222. Thenetwork interface device 208 can include an analog modem, ISDN modem,cable modem, token ring interface, satellite transmission interface(e.g. “direct PC”), or other interfaces for coupling computer system 222to other computer systems (e.g., remote processor server 206). Thenetwork interface device 208 can include one or more input and/or output(I/O) devices. The I/O devices can include, by way of example but notlimitation, a keyboard, a mouse or other pointing device, disk drives,printers, a scanner, and other input and/or output devices, includingdisplay device 212. The display device 212 can include, by way ofexample but not limitation, a cathode ray tube (CRT), liquid crystaldisplay (LCD), or some other applicable known or convenient displaydevice. For simplicity, it is assumed that controllers of any devicesnot depicted in the example of FIG. 2 reside in the transceiver system101.

In operation, the computer system 222 can be controlled by operatingsystem software that includes a file management system, such as a diskoperating system. One example of operating system software withassociated file management system software is the family of operatingsystems known as Windows® from Microsoft Corporation of Redmond, Wash.,and their associated file management systems. Another example ofoperating system software with its associated file management systemsoftware is the Linux operating system and its associated filemanagement system. The file management system is typically stored innon-volatile portions of memory 204 and/or drive unit, and causes theprocessor 202 to execute the various acts required by the operatingsystem to input and output data and to store data in the memory 204,including storing files on the non-volatile memory and/or drive unit.

FIG. 3 is a block diagram illustrating an example client power receiver103 in accordance with one or more embodiments. Client power receiver103 may include various functional components such as analog and digitalelectronic devices or modules may be electrically and/or communicativelycoupled together. The functional components of client power receiver 103include a controller 301 having control logic 302 and data storage media303. Client power receiver 103 also includes a battery 304, acommunication block 306 and an associated first antenna 308, a powermeter 310, a rectifier 312, a beacon signal generator 314 and anassociated second antenna 316, and a switch 318 alternately coupling therectifier 312 and the beacon signal generator 314 to an associated thirdantenna 320. Some or all of the above listed components of client powerreceiver 103 can be omitted in some embodiments. Additional or fewercomponents are also possible. For example, some embodiments of clientdevices 102 may also include accelerometers to measure acceleration ofthe device or a global positioning system that can identify the globalpositioning coordinates of the receiver and estimate current velocity.

The rectifier 312 receives (e.g., via the third antenna 320) a powertransmission signal 322 from the transceiver system 101, which is fedthrough the power meter 310 to the battery 304 for charging. The powermeter 310 measures the total received power signal strength and providesthe control logic 302 with this measurement. The control logic 302 canalso receive the battery power level from the battery 304 itself orreceive battery power level data from, for example, an applicationprogramming interface (API) of an operating system running on the clientdevice 102. The control logic 302 can also transmit/receive, via thecommunication block 306, a data signal on a data carrier frequency, suchas the base signal clock for clock synchronization.

Using the second 316 and/or third 320 antennas, the beacon signalgenerator 314 transmits a beacon signal 324 or a calibration signal 326to transceiver system 101. Furthermore, in the example embodiment,battery 304, and the first 308, second 316, and third 320 antennas arepositioned in the client device 102. In other embodiments, at least oneof the battery 304, and the first 308, second 316, and third 320antennas are positioned in the client device 102. For example, andwithout limitation, some embodiments of client power receiver 103 caninclude a dedicated power supply such as a battery cell that may or maynot be rechargeable through rectifier 312 and/or a plug-in chargercircuit of the client power receiver 103. Thus, in such otherembodiments, during such times when client device 102 is powered off,components of the system may remain fully capable of using the second316 and/or third 320 antennas to transmit beacon signal 324 and/orcalibration signal 326, as well as receive power transmission signal322, for purposes of client device 102 localization and/or wirelesspower transmission system based battery 304 charging. At least one ofthe first 308, second 316, and third 320 antennas also enable clientdevice to Tx/Rx a data signal 327 to/from transceiver system 101.

Although the battery 304 shown in FIG. 3 is charged via WPTS through thecircuit including rectifier 312, the client power receiver 103 can alsoreceive its supply power directly from the rectifier 312 instead of, orin addition to client power receiver 103 being powered by battery 304.Also, it can be noted that the use of multiple antennas (e.g., antennas308, 316, and 320) is one example of implementation of client device 102and as such, the structure can be reduced to one shared antenna, wherethe client device 102 multiplexes signal reception and transmission.

Client device 102 can also include a motion sensor 328 capable ofdetecting motion and signaling the control logic 302 of a motion eventof client device 102. Client power receiver 103 can also integrateadditional motion detection mechanisms such as accelerometers, assistedglobal positioning system (GPS), or other mechanisms. Once motion sensor328 determines the motion event, control logic 302 assumes that themotion event equates to the client device 102. Control logic 302 thensignals the transceiver system 101 modify the power transmission. Incases where the client power receiver 103 is used in a movingenvironment like a transceiver system 101-equipped vehicle, power may betransmitted intermittently or at a reduced level until the device isclose to losing all available power. Motion sensor 328, as well as theaforementioned additional motion detection mechanisms may be integratedinto client device 102.

FIG. 4 depicts a sequence diagram 400 illustrating an example ofoperations between a wireless power delivery system (e.g., WPTS 101) anda wireless power receiver client (e.g., wireless power receiver client103) for establishing wireless power delivery in a multipath wirelesspower delivery, according to various embodiments. Initially,communication is established between the wireless power transmissionsystem 101 and the power receiver client 103. The initial communicationcan be, for example, a data communication link that is established viaone or more antennas 104 of the wireless power transmission system 101.In some embodiments, one or more of the antennas 104 a-104 n can be dataantennas, wireless power transmission antennas, or dual-purposedata/power antennas. Various information can be exchanged between thewireless power transmission system 101 and the wireless power receiverclient 103 over this data communication channel. For example, wirelesspower signaling can be time sliced among various clients in a wirelesspower delivery environment. In such cases, the wireless powertransmission system 101 can send beacon schedule information, e.g.,Beacon Beat Schedule (BBS) cycle, power cycle information, etc., so thatthe wireless power receiver client 103 knows when to transmit(broadcast) its beacon signals and when to listen for power, etc.

Continuing with the example of FIG. 4, the wireless power transmissionsystem 101 selects one or more wireless power receiver clients forreceiving power and sends the beacon schedule information to the selectwireless power receiver clients 103. The wireless power transmissionsystem 101 can also send power transmission scheduling information sothat the wireless power receiver client 103 knows when to expect (e.g.,a window of time) wireless power from the wireless power transmissionsystem. The wireless power receiver client 103 then generates a beacon(or calibration) signal and broadcasts the beacon during an assignedbeacon transmission window (or time slice) indicated by the beaconschedule information, e.g., Beacon Beat Schedule (BBS) cycle. Asdiscussed herein, the wireless power receiver client 103 includes one ormore antennas (or transceivers) which have a radiation and receptionpattern in three-dimensional space proximate to the wireless device 102in which the wireless power receiver client 103 is embedded.

The wireless power transmission system 101 receives the beacon from thepower receiver client 103 and detects and/or otherwise measures thephase (or direction) from which the beacon signal is received atmultiple antennas. In accordance with some embodiments, wireless powertransmission system 101 can record the arrival time diversity (e.g.,different phase of arrivals at the same antenna). This information canbe used to activate antennas to transmit outgoing signals in a staggeredtiming to compensate for the propagation delay in the different paths.In some embodiments, the signals may be processed to remove side echoesand the transmission schedule adjusted accordingly.

The wireless power transmission system 101 then delivers wireless powerto the power receiver client 103 from the multiple antennas 103 based onthe detected or measured phase (or direction) of the received beacon ateach of the corresponding antennas by activating the antennas in areversed (or nearly reversed order). In some embodiments, the wirelesspower transmission system 101 determines the complex conjugate of themeasured phase of the beacon and uses the complex conjugate to determinea transmit phase that configures the antennas for delivering and/orotherwise directing wireless power to the wireless power receiver client103 via the same path over which the beacon signal was received from thewireless power receiver client 103.

In some embodiments, the wireless power transmission system 101 includesmany antennas. One or more of the many antennas may be used to deliverpower to the power receiver client 103. The wireless power transmissionsystem 101 can detect and/or otherwise determine or measure phases atwhich the beacon signals are received at each antenna. The large numberof antennas may result in different phases of the beacon signal beingreceived at each antenna of the wireless power transmission system 101.

As discussed above, the wireless power transmission system 101 candetermine the complex conjugate of the beacon signals received at eachantenna. Using the complex conjugates, one or more antennas may emit asignal that takes into account the effects of the large number ofantennas in the wireless power transmission system 101. In other words,the wireless power transmission system 101 can emit a wireless powertransmission signal from the one or more antennas in such a way as tocreate an aggregate signal from the one or more of the antennas thatapproximately recreates the waveform of the beacon in the oppositedirection. Said another way, the wireless power transmission system 101can deliver wireless RF power to the wireless power receiver clients viathe same paths over which the beacon signal is received at the wirelesspower transmission system 101. These paths can utilize reflectiveobjects 106 within the environment. Additionally, the wireless powertransmission signals can be staggered and/or simultaneously transmittedfrom the wireless power transmission system 101 such that the wirelesspower transmission signals collectively match the antenna radiation andreception pattern of the client device in a three-dimensional (3D) spaceproximate to the client device.

As shown, the beacon (or calibration) signals can be periodicallytransmitted by wireless power receiver clients 103 within the powerdelivery environment according to, for example, the BBS, so that thewireless power transmission system 101 can maintain knowledge and/orotherwise track the location of the power receiver clients 103 in thewireless power delivery environment. The process of receiving beaconsignals from a wireless power receiver client 103 at the wireless powertransmission system and, in turn, responding with wireless powerdirected to that particular wireless power receiver client is referredto herein as retrodirective wireless power delivery.

FIG. 5 illustrates an example multipath wireless power deliveryenvironment 500 according to some embodiments. As illustrated in FIG. 5,a wireless device 502 delivering power to WPTS 101 having multipleantennas 504. The multipath wireless power delivery environment 500 canincludes reflective objects (not shown) and various absorptive objects,e.g., users, or humans, furniture, etc. As a result, multiple pathsP1-P4 may exist between wireless device 502 and antennas 504. Thewireless device 502 transmits a beacon (or calibration) signal overmultiple paths to the wireless power transmission system 501. Thewireless device 502 can transmit a beacon in the direction of aradiation and reception pattern such that the strength of the receivedbeacon signal by the wireless power transmission system, e.g., receivedsignal strength indication (RSSI), depends on the radiation andreception pattern. For example, beacon signals are not transmitted wherethere are nulls in the radiation and reception pattern and beaconsignals are the strongest at the peaks in the radiation and receptionpattern, e.g., peak of the primary lobe. As shown in the example of FIG.5, the wireless device 502 transmits beacon signals over four paths eachhaving different propagation delays compared to the line of sight path.

The wireless power transmission system 501 receives beacon signals ofincreasing strengths via paths. In some embodiments, the beacon signalsare directionally transmitted in this manner, for example, to avoidunnecessary RF energy exposure to the user. A fundamental property ofantennas is that the receiving pattern (sensitivity as a function ofdirection) of an antenna when used for receiving is identical to thefar-field radiation pattern of the antenna when used for transmitting.This is a consequence of the reciprocity theorem in electromagnetism.

The wireless power transmission system 101 receives the beacon (orcalibration) signal via multiple paths P1-P4 at multiple antennas ortransceivers. As shown, path P3 is a direct line of sight path whilepaths P1, P2, and P4 are non-line of sight paths. Once the beacon (orcalibration) signal is received by the wireless power transmissionsystem 501, the power transmission system 501 processes the beacon (orcalibration) signal to determine arrival times of the beacon signal ateach of the multiple antennas 504 and the phases at which the beaconsignal is received at each of the multiple antennas or transceivers.Then, power transmission system 501 can reverse time (e.g., −t), for thetransmission signal to generate the power transmission signal. Thefollowing is a simplified mathematical signal model for four pathpropagation channels illustrated in FIG. 4 in which time-reversed. Bytime reversal, there is a possibility to coherently combine differentarrivals of the outgoing signal (time-reversed version of incomingbeacon) at some point.

BeaconingA(t)=C(t)+C(t−τ ₁)+C(t−τ ₂)+C(t−τ ₃)Power DeliveryR(t)=T(t)+T(t−τ ₁)+T(t−τ ₂)+T(t−τ ₃)whereT(t)=A(−t)=C(−t)+C(−t−τ ₁)+C(−t−τ ₂)+C(−t−τ ₃)Power ReceivedR(t)=C(−t)+C(−t−τ ₁)+C(−t−τ ₂)+C(−t−τ ₃)+C(−t−τ ₁)+C(−t)+C(−t+τ₁−τ₂)+C(−t+τ ₁−τ₃)+C(−t−τ ₂)+C(−t+τ ₂−τ₁)+C(−t)+C(−t+τ₂−τ₃)+C(−t)+C(−t+τ ₃−τ₁)+C(−t+τ ₃−τ₂)+C(−t)

In accordance with various embodiments, these time reversal techniquescan be augmented to traditional phased-array techniques such asbeamforming, retrodirective arrays, and the like. In addition, eachantenna effectively acts as multiple virtual antennas (e.g., in the timedomain). The spacing may be uniform, patterned, non-uniform, or random.Time reversal techniques (e.g., capturing the incoming RF beacons andamplifying/playing back) is one among possibly other implementationsthat tries to take opportunistic approach to utilize the delay spread ofthe channel. It is conjectured, if the charger estimates the fullchannel response, there are more-matched waveforms with less potentiallydestructive effects on the side-echoes.

Various measurement results show that for most office buildings, thedelay spread is the range of 40 to 70 ns, while larger delay spreads upto 300 ns can be expected in large buildings like shopping centers andfactories. The average received multipath power is an exponentiallydecaying function of the excess delay. Further, the amplitudes ofindividual multipath components are Rayleigh distributed. Even smallrooms (5 m×5 m) can give significant delay spreads around 50 ns whenthere are metal walls. For frequencies around 2 and 5 GHz, the mediandelay spread is the 50% value, meaning that 50% of all channels has adelay spread that is lower than the median value.

Measurements done at several frequencies simultaneously show that thereis no significant difference in the delay spreads when the frequencychanges from 850 MHz to 4 GHz. In some embodiments, at least a portionof the signal (e.g., 40-100 ns) can be recorded to get the idea aboutthe channel response we need 1 ns synchronicity if beacon is shortpulse. For wideband pulse (e.g., tone-like), the recording times may beable to be relaxed.

FIG. 6 is a flowchart illustrating a set of operations 600 for operatinga wireless communication/power delivery system in accordance with someembodiments of the present technology. As illustrated in FIG. 6,monitoring operation 610 monitors incoming signals from a client device.The signal may be a beaconing signal, a calibration signal or some othertype of communications. Identification operation 615 can identifyincoming arrival times from multiple paths at one or more differentantennas. This can be used to create a response profile for generating aresponse to the incoming signal. Determination operation 620 determineswhether a response is needed. If no response is needed, thendetermination operation 620 branches to monitoring operation 610 wherethe system monitors for additional incoming signals. If no response isneeded, then determination operation 620 branches to response operation625 where an appropriate response is created. Timing operation 630identifies a radiation pattern for the response signal. Then activationoperation 635 can set antenna activation based on a reversed timing ofthe incoming signal.

FIG. 7 is a sequence diagram illustrating an example of the data flowbetween various components of a wireless power transmission systemaccording to various embodiments of the present technology. Asillustrated in FIG. 7, monitoring system 710 monitors for a set ofincoming signals. Monitoring system 710 can record or store at least aportion of the incoming signal. Control circuitry 720, upon receiving anotification of the recordation, initiate a time reversal processing bysignal generator 730. For example, signal generator 730 can use therecorded signal to generate a response signal that effectively reversesthe timing of the incoming signal. This response signal can then betransmitted by transceivers 740.

Exemplary Computer System Overview

FIG. 8 depicts a diagrammatic representation of a machine, in theexample form, of a computer system within which a set of instructions,for causing the machine to perform any one or more of the methodologiesdiscussed herein, may be executed.

In the example of FIG. 8, the computer system includes a processor,memory, non-volatile memory, and an interface device. Various commoncomponents (e.g., cache memory) are omitted for illustrative simplicity.The computer system 800 is intended to illustrate a hardware device onwhich any of the components depicted in the example of FIG. 1 (and anyother components described in this specification) can be implemented.For example, the computer system can be any radiating object or antennaarray system. The computer system can be of any applicable known orconvenient type. The components of the computer system can be coupledtogether via a bus or through some other known or convenient device.

The processor may be, for example, a conventional microprocessor such asan Intel Pentium microprocessor or Motorola power PC microprocessor. Oneof skill in the relevant art will recognize that the terms“machine-readable (storage) medium” or “computer-readable (storage)medium” include any type of device that is accessible by the processor.

The memory is coupled to the processor by, for example, a bus. Thememory can include, by way of example but not limitation, random accessmemory (RAM), such as dynamic RAM (DRAM) and static RAM (SRAM). Thememory can be local, remote, or distributed.

The bus also couples the processor to the non-volatile memory and driveunit. The non-volatile memory is often a magnetic floppy or hard disk, amagnetic-optical disk, an optical disk, a read-only memory (ROM), suchas a CD-ROM, EPROM, or EEPROM, a magnetic or optical card, or anotherform of storage for large amounts of data. Some of this data is oftenwritten, by a direct memory access process, into memory during executionof software in the computer 800. The non-volatile storage can be local,remote, or distributed. The non-volatile memory is optional becausesystems can be created with all applicable data available in memory. Atypical computer system will usually include at least a processor,memory, and a device (e.g., a bus) coupling the memory to the processor.

Software is typically stored in the non-volatile memory and/or the driveunit. Indeed, for large programs, it may not even be possible to storethe entire program in the memory. Nevertheless, it should be understoodthat for software to run, if necessary, it is moved to a computerreadable location appropriate for processing, and for illustrativepurposes, that location is referred to as the memory in this document.Even when software is moved to the memory for execution, the processorwill typically make use of hardware registers to store values associatedwith the software, and local cache that, ideally, serves to speed upexecution. As used herein, a software program is assumed to be stored atany known or convenient location (from non-volatile storage to hardwareregisters) when the software program is referred to as “implemented in acomputer-readable medium”. A processor is considered to be “configuredto execute a program” when at least one value associated with theprogram is stored in a register readable by the processor.

The bus also couples the processor to the network interface device. Theinterface can include one or more of a modem or network interface. Itwill be appreciated that a modem or network interface can be consideredto be part of the computer system. The interface can include an analogmodem, ISDN modem, cable modem, token ring interface, satellitetransmission interface (e.g. “direct PC”), or other interfaces forcoupling a computer system to other computer systems. The interface caninclude one or more input and/or output devices. The I/O devices caninclude, by way of example but not limitation, a keyboard, a mouse orother pointing device, disk drives, printers, a scanner, and other inputand/or output devices, including a display device. The display devicecan include, by way of example but not limitation, a cathode ray tube(CRT), liquid crystal display (LCD), or some other applicable known orconvenient display device. For simplicity, it is assumed thatcontrollers of any devices not depicted in the example of FIG. 8 residein the interface.

In operation, the computer system 800 can be controlled by operatingsystem software that includes a file management system, such as a diskoperating system. One example of operating system software withassociated file management system software is the family of operatingsystems known as Windows® from Microsoft Corporation of Redmond, Wash.,and their associated file management systems. Another example ofoperating system software with its associated file management systemsoftware is the Linux operating system and its associated filemanagement system. The file management system is typically stored in thenon-volatile memory and/or drive unit and causes the processor toexecute the various acts required by the operating system to input andoutput data and to store data in the memory, including storing files onthe non-volatile memory and/or drive unit.

Some portions of the detailed description may be presented in terms ofalgorithms and symbolic representations of operations on data bitswithin a computer memory. These algorithmic descriptions andrepresentations are the means used by those skilled in the dataprocessing arts to most effectively convey the substance of their workto others skilled in the art. An algorithm is here, and generallyconceived to be a self-consistent sequence of operations leading to adesired result. These operations are those requiring physicalmanipulations of physical quantities. Usually, though not necessarily,these quantities take the form of electrical or magnetic signals capableof being stored, transferred, combined, compared, and otherwisemanipulated. It has proven convenient at times, principally for reasonsof common usage, to refer to these signals as bits, values, elements,symbols, characters, terms, numbers, or the like.

It should be borne in mind, however, that all of these and similar termsare to be associated with the appropriate physical quantities and aremerely convenient labels applied to these quantities. Unlessspecifically stated otherwise, as apparent from the followingdiscussion, it is appreciated that throughout the description,discussions utilizing terms such as “processing” or “computing” or“calculating” or “determining” or “displaying” or the like, refer to theaction and processes of a computer system, or similar electroniccomputing device, that manipulates and transforms data represented asphysical (electronic) quantities within the computer system's registersand memories into other data similarly represented as physicalquantities within the computer system memories or registers or othersuch information storage, transmission or display devices.

The algorithms and displays presented herein are not inherently relatedto any particular computer or other apparatus. Various general-purposesystems may be used with programs in accordance with the teachingsherein, or it may prove convenient to construct more specializedapparatus to perform the methods of some embodiments. The requiredstructure for a variety of these systems will appear from thedescription below. In addition, the techniques are not described withreference to any particular programming language, and variousembodiments may thus be implemented using a variety of programminglanguages.

In alternative embodiments, the machine operates as a standalone deviceor may be connected (e.g., networked) to other machines. In a networkeddeployment, the machine may operate in the capacity of a server or aclient machine in a client-server network environment or as a peermachine in a peer-to-peer (or distributed) network environment.

The machine may be a server computer, a client computer, a personalcomputer (PC), a tablet PC, a laptop computer, a set-top box (STB), apersonal digital assistant (PDA), a cellular telephone, an iPhone, aBlackberry, a processor, a telephone, a web appliance, a network router,switch or bridge, or any machine capable of executing a set ofinstructions (sequential or otherwise) that specify actions to be takenby that machine.

While the machine-readable medium or machine-readable storage medium isshown in an exemplary embodiment to be a single medium, the term“machine-readable medium” and “machine-readable storage medium” shouldbe taken to include a single medium or multiple media (e.g., acentralized or distributed database, and/or associated caches andservers) that store the one or more sets of instructions. The term“machine-readable medium” and “machine-readable storage medium” shallalso be taken to include any medium that is capable of storing, encodingor carrying a set of instructions for execution by the machine and thatcause the machine to perform any one or more of the methodologies of thepresently disclosed technique and innovation.

In general, the routines executed to implement the embodiments of thedisclosure, may be implemented as part of an operating system or aspecific application, component, program, object, module or sequence ofinstructions referred to as “computer programs.” The computer programstypically comprise one or more instructions set at various times invarious memory and storage devices in a computer, and that, when readand executed by one or more processing units or processors in acomputer, cause the computer to perform operations to execute elementsinvolving the various aspects of the disclosure.

Moreover, while embodiments have been described in the context of fullyfunctioning computers and computer systems, those skilled in the artwill appreciate that the various embodiments are capable of beingdistributed as a program product in a variety of forms, and that thedisclosure applies equally regardless of the particular type of machineor computer-readable media used to actually effect the distribution.

Further examples of machine-readable storage media, machine-readablemedia, or computer-readable (storage) media include but are not limitedto recordable type media such as volatile and non-volatile memorydevices, floppy and other removable disks, hard disk drives, opticaldisks (e.g., Compact Disk Read-Only Memory (CD ROMS), Digital VersatileDisks, (DVDs), etc.), among others, and transmission type media such asdigital and analog communication links.

CONCLUSION

Unless the context clearly requires otherwise, throughout thedescription and the claims, the words “comprise,” “comprising,” and thelike are to be construed in an inclusive sense, as opposed to anexclusive or exhaustive sense; that is to say, in the sense of“including, but not limited to.” As used herein, the terms “connected,”“coupled,” or any variant thereof means any connection or coupling,either direct or indirect, between two or more elements; the coupling orconnection between the elements can be physical, logical, or acombination thereof. Additionally, the words “herein,” “above,” “below,”and words of similar import, when used in this application, refer tothis application as a whole and not to any particular portions of thisapplication. Where the context permits, words in the above DetailedDescription using the singular or plural number may also include theplural or singular number respectively. The word “or,” in reference to alist of two or more items, covers all of the following interpretationsof the word: any of the items in the list, all of the items in the list,and any combination of the items in the list.

The above Detailed Description of examples of the technology is notintended to be exhaustive or to limit the technology to the precise formdisclosed above. While specific examples for the technology aredescribed above for illustrative purposes, various equivalentmodifications are possible within the scope of the technology, as thoseskilled in the relevant art will recognize. For example, while processesor blocks are presented in a given order, alternative implementationsmay perform routines having steps, or employ systems having blocks, in adifferent order, and some processes or blocks may be deleted, moved,added, subdivided, combined, and/or modified to provide alternative orsubcombinations. Each of these processes or blocks may be implemented ina variety of different ways. Also, while processes or blocks are attimes shown as being performed in series, these processes or blocks mayinstead be performed or implemented in parallel, or may be performed atdifferent times. Further any specific numbers noted herein are onlyexamples: alternative implementations may employ differing values orranges.

The teachings of the technology provided herein can be applied to othersystems, not necessarily the system described above. The elements andacts of the various examples described above can be combined to providefurther implementations of the technology. Some alternativeimplementations of the technology may include not only additionalelements to those implementations noted above, but also may includefewer elements.

These and other changes can be made to the technology in light of theabove Detailed Description. While the above description describescertain examples of the technology, and describes the best modecontemplated, no matter how detailed the above appears in text, thetechnology can be practiced in many ways. Details of the system may varyconsiderably in its specific implementation, while still beingencompassed by the technology disclosed herein. As noted above,particular terminology used when describing certain features or aspectsof the technology should not be taken to imply that the terminology isbeing redefined herein to be restricted to any specific characteristics,features, or aspects of the technology with which that terminology isassociated. In general, the terms used in the following claims shouldnot be construed to limit the technology to the specific examplesdisclosed in the specification, unless the above Detailed Descriptionsection explicitly defines such terms. Accordingly, the actual scope ofthe technology encompasses not only the disclosed examples, but also allequivalent ways of practicing or implementing the technology under theclaims.

To reduce the number of claims, certain aspects of the technology arepresented below in certain claim forms, but the applicant contemplatesthe various aspects of the technology in any number of claim forms. Forexample, while only one aspect of the technology is recited as acomputer-readable medium claim, other aspects may likewise be embodiedas a computer-readable medium claim, or in other forms, such as beingembodied in a means-plus-function claim. Any claims intended to betreated under 35 U.S.C. § 112(f) will begin with the words “means for”,but use of the term “for” in any other context is not intended to invoketreatment under 35 U.S.C. § 112(f). Accordingly, the applicant reservesthe right to pursue additional claims after filing this application topursue such additional claim forms, in either this application or in acontinuing application.

What is claimed is:
 1. A method comprising: sampling at least a portionof a wireless signal received from a client device at a first, and atleast a second, antenna of an antenna array; generating, based on thesampling, an arrival profile for the wireless signal; determining, basedon the sampling, response signals for transmission by the first, and theat least a second, antenna; and transmitting the response signals to theclient device, wherein the determining step comprises identifying atransmission timing sequence for the first, and the at least a second,antenna for the transmitting step.
 2. The method of claim 1, wherein thegenerating step comprises generating the arrival profile for thewireless signal in the absence of time of arrival measurements.
 3. Themethod of claim 1, wherein the transmitting step comprises: firsttransmitting a first response signal using the first antenna to theclient device on a first propagation path; and after the firsttransmitting step, second transmitting a second response signal usingthe at least a second antenna to the client device on a secondpropagation path, wherein the first propagation path is longer than thesecond propagation path.
 4. The method of claim 1, further comprisingcausing, by the transmitting step, the response signals to arrive at theclient device at the same time.
 5. The method of claim 1, wherein thesampling step comprises: sampling a first wireless signal received atthe first antenna from a first client device; and sampling a secondwireless signal received at the at least a second antenna from a secondclient device.
 6. The method of claim 5, wherein the transmitting stepcomprises: transmitting a first response signal to the first clientdevice using the first antenna; and transmitting a second responsesignal to the second client device using the second antenna.
 7. Themethod of claim 5, wherein the determining step comprises: determining afirst response signal for transmission by the first antenna; anddetermining a second response signal for transmission by the secondantenna.
 8. A system comprising: an antenna array; and control circuitrycoupled to the antenna array and configured to: sample at least aportion of a wireless signal received from a client device at a first,and at least a second, antenna of the antenna array; generate, based onone or more results of the sampling, an arrival profile for the wirelesssignal; determine, based on the arrival profile, response signals fortransmission by the first, and the at least a second, antenna; and causethe response signals to be transmitted to the client device, wherein todetermine response signals, the control circuitry is further configuredto identify a transmission timing sequence for the first, and the atleast a second, antenna for causing the response signals to betransmitted to the client device.
 9. The system of claim 8, wherein thewireless signal is received from the client device via multiplepropagation paths having at least two differing path lengths.
 10. Thesystem of claim 8, wherein the control circuitry is further configuredto sample the at least a portion of the wireless signal in the timedomain.
 11. The system of claim 8, wherein to determine response signalsthe control circuitry is further configured to identify, for the first,and the at least a second, antenna, a radiation pattern for the responsesignals.
 12. The system of claim 8, wherein the wireless signal includesa communications signal.
 13. The system of claim 8, wherein the antennaarray includes an adaptively-phased array.
 14. The system of claim 8,wherein the response signal includes a wireless power transmissionsignal.
 15. One or more non-transitory computer-readable storage mediahaving executable code stored thereon that when executed by at least oneprocessor causes a machine to: sample at least a portion of a wirelesssignal received from a client device at a first, and at least a second,antenna of an antenna array; generate, based on samples of the wirelesssignal, an arrival profile for the wireless signal; determine, based onthe arrival profile, response signals for transmission by the first, andthe at least a second, antenna; and cause the response signals to betransmitted to the client device, wherein when executed by the at leastone processor to determine the response signals, the executable codefurther causes the machine to identify a transmission timing sequencefor the first, and the at least a second, antenna for causing theresponse signals to be transmitted to the client device.
 16. The one ormore non-transitory computer readable storage media of claim 15,wherein: when executed by the at least one processor to generate thearrival profile, the executable code further causes the machine toidentify magnitudes of the wireless signal received at the first, andthe at least a second, antenna; and when executed by the at least oneprocessor to determine response signals, the executable code furthercauses the machine to adjust a magnitude of a response signal fortransmission by one or more of the first, and the at least a second,antenna.
 17. The one or more non-transitory computer readable storagemedia of claim 15, wherein: when executed by the at least one processorto generate the arrival profile, the executable code further causes themachine to identify phases of the wireless signal received at the first,and the at least a second, antenna; and when executed by the at leastone processor to determine response signals, the executable code furthercauses the machine to adjust a phase of a response signal fortransmission by one or more of the first, and the at least a second,antenna.
 18. The one or more non-transitory computer readable storagemedia of claim 15, wherein when executed by the at least one processorto cause the response signals to be transmitted to the client device,the executable code further causes the machine to generate a coherenttransmission signal representing a time reversed version of the wirelesssignal received at the first, and the at least a second, antenna. 19.The one or more non-transitory computer readable storage media of claim15, wherein when executed by the at least one processor to generate thearrival profile, the executable code further causes the machine togenerate the arrival profile for the wireless signal in the absence oftime of arrival measurements.
 20. The one or more non-transitorycomputer readable storage media of claim 15, wherein when executed bythe at least one processor, the executable code further causes themachine to schedule transmission of the response signals according todata encoded by the wireless signal.